THE ALCOHOL TEST IN RELATION TO MILK. 
11 
the acidity to 2.55 and yet the alcohol test was negative. When 7 
c. c. of N/10 lactic acid was added to the normal milk, the acidity was 
increased to 3.00 and the milk coagulated with large flakes with all 
the different percentages of alcohol. When 7 c. c. of N/10 lactic 
acid was added to milk with dibasic phosphate the acidity was 
increased to 3.05 and only the 75 per cent alcohol test was positive, 
and the coagulation was in the form of small flakes. When 8 c. c. 
of acid was added to the milk with dibasic phosphate the acidity 
was 3.19 and the alcohol test with both 75 per cent and 68 per cent 
alcohol was positive. It was found by titration that 10 c. c. of a 
0.5 solution of dibasic phosphate required 1.56 c. c. of N/10 lactic 
acid to convert the dibasic into the monobasic phosphate; therefore 
50 c. c. of milk containing 0.5 per cent of dibasic sodium phosphate 
would require 7.8 c. c. of N/10 lactic acid to convert the dibasic 
into the monobasic phosphate. It will be seen from Table 6 that 
when from 7 to 8 c. c. of N/10 lactic acid was added to the milk 
with dibasic phosphate, the alcohol test became positive; that is, when 
the dibasic phosphate had been converted into monobasic phosphate 
then further increase in acidity caused a positive alcohol test. 
As a very general explanation of this result it may be said that when 
acid is added to milk it converts the dibasic phosphate into the 
monobasic phosphate. It follows that the acid and also the monobasic 
phosphate probably affect the casein and thereby change it into a 
condition in which it is possible to precipitate the casein by alcohol 
and cause a positive test. This action on the dibasic phosphate prob- 
ably explains in part the positive alcohol tests with different low 
acidities. 
Table 6. — Influence on the alcohol test of the addition of dibasic phosphate to milk. 
Normal milk. 
Normal milk + 0.5 per cent 
N/10 
dibasic sodium phosphate. 
lactic 
acid 
added 
Alcohol test. 
Alcohol test. 
to 
50 c. c. 
of 
Acidity. 
75 
68 
44 
Acidity. 
75 
68 
44 
milk. 
per 
per 
per 
per 
per 
per 
cent. 
cent. 
cent. 
cent. 
cent. 
cent. 
c. c. 

1.85 
2.03 
1 
2.01 
1 +s 
— 
— 
2.13 
_ 
_ 
_ 
3 
2.37 
+L 
+ M 
— 
2.55 
— 
_ 
_ 

2.63 
+ L 
+ L 
+s 
2.81 
— 
— 
— 
6 
2.80 
+ L 
+ L 
+M 
2.92 
_ 
_ 
_ 
7 
3.00 
+ L 
+ L 
+ L 
3.05 
+s 
— 
— 
8 
3. 19 
+ L 
+M 
9 
3.43 
+ L 
+ L 
_ 
11 
3.97 
+ L 
+ L 
+ L 
1 See footnote under Table 1. 
